Not "infinity"--"zero"!

For some reason, when we told gevent to wait for an infinite amount of
time between calls, it decided that meant "wait no time at all", and
thus the method in question would run whenever gevent yielded. (I think
that's the right term here.) That would be wrong on gevent's part, and it
was fixed in gevent in Python 3, as far as we can tell.

Unfortunately, when we told it to wait for an infinite number of seconds
in this test, we actually *did* want the "0" behavior. So this change
explicitly sets it to that.
Python 3 changes

As always, the usual stuff: "when I say 'range' use 'xrange'", that
sort of thing. Also a change to "callable()"; and it turns out that
the tests want the monkey.patch_all() to be called in setup, and
not before setup.

Also took this chance to remove some debugging print-statements
that were commented out.